Brush and method of manufacturing the same



H. H. WIKLE.

BRUSH AND METHOD OF MANUFACTURING THE SAME.

APPLICATION FILED APR. 13, 191B.

Patented Apr. 26, 1921.

fizzzeniar UNITED STATES;

HUGH H. WIKLE, 0115 CHICAGO, ILLINOIS.

BRUSH AND METHOD OF MANUFACTURING THE SAME.

Application filed Apri113,

To all whom it may concern: Be it known that I, HUGH H. WIKLE, a citizen of the United States, residing at Chicago, in theoounty of Cook and State of Illinois, have invented a certain new and useful Improvement in Brushes'and Methods of Manufacturing the Same, ofwhich the following is a full, clear, concise, and ex-' act description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to the manufacture of brushes for electrical machinery.

Whereas certain of the steps involved in this invention are novel in and of themselves and may be applied to other purposes, I disclose and claim the same in certain 00- pending applications, to-wit Serial No. 228,310, filed April 1a, 1918, and Serial No. 250,416, filed August19, 1918.

The particular type of brushes to which this invention relates isthe rigid or block type of brush formed of a mixture of some metal, preferably including copper and some form of carbon, preferably graphite. These brushes are of two kinds well recognized in the art as the metal brush, which consists of a mixture of finely divided metal and graphite with no further binder, and the metal-graphite brush, which consists of a mixture of finely divided metal and graph ite with a binder. c 1 I The metal brush looks much like the metal from which it is formed. It is lighter than metal containing about 90% of metal and 10% of graphite by weight. The metalgraphite brush appears nearly black, though it shows the metal. in its "structure. The proportions of metal in the brush may vary considerably, according to grade, but they run from 20% to 80% by weight. 'The binder, which is usually pitch, enters into the batch or mix approximately to the extent of 20% by weight.

Heretofore the manufacture ofbrushes of this type has been practised by employing mechanically powdered or pulverized metal; Mechanical pulverization isexpensive and difiicult and provides-only a relatively coarse powder.

According-to my invention the powdered metal is produced electro-chemically'. Not only is this done at less expense, but less labor and difliculty isinvolved and the re- Speeification of Letters Patent.

Patented Apr. 26, 1921.

1918. Serial No. 228,309.

Another advantage is the fact that the danger from ii in dust is reatl reduced if not wholly eliminated. y Certain other advantages and objects will appear from the following specification;

In the accompanying drawings which form a part of the present specification, I have illustrated diagrammatically the steps which enter intothe manufacture of a brush according to my invention.

Flgure 1 1s a diagram of the electrolytic vat and filter for precipitating and separatmg cuprous oxid.

F ig. 2 diagrammatically indicates the step of mixing the cuprous oxid with graphite; Fig. 3 is a sectional view of the furnace employed to pre-bake the mix where a hydro-carbon binder such as pitch is employed; F igt 4 illustrates a hydraulic press for preissing the mixture into slabs or blocks; an

Fig. 5 is a sectional view of a furnace'for .baking the blocks or plates to drive off the remaining hydrocarbons and sintering the particles of metal together.

The .first step of my invention is a novel method of securing finely divided copper oxid. For the purposes of the present invention the oxid might be obtained in any desired manner, but I shall describe briefly the manner in which I obtain the same, although this particular mechanism and process is. described more fully and claimed in my co-pending application, Serial Number 228,310, above referred to.

The electrodes 1 and .2 are of similar metal. I have found that electrodes of copper, brass, bronze or the like may be employed successfully, but shall' limit the present description to the use of copper in commercial form.- The copper electrodes 1 I and 2 are suspended in an electrolyte 3,

which comprises a saturated solution of sodium chlorid. A suitable vat; 4, having a draw-off connection 5, 'controlledby a valve 6, forms the container for the electrolyte.

The electrodes 1 and 2 are connected through a reversing switch 7 to a suitable source of current 8. A suitable filter -9 is placed so as to receive'the discharge of liquidand precipitate "from the vat 4:. This-filter comprises an open bottomed box. 10, having a suitable fil-- ter, preferably made of cloth, stretched across the bottom as shown at 11 in Fig. 1.. The filter '9 is removable from the box or tank 12, over which it is normally held.

The liquidwith the precipitate is discharged a into the filter'9 and the. liquid then passes through into the tank 12 from whence it'is "conveyed" by the pipe 13 and pump 14: back to the vat 4i by way of the discharge pipe '15. The chemical'action of the electrodes and N electrolyte.iscontinuous. The electrolyte of sodium chlorid is electrolyzed, the ions of 7 sodium uniting with thewater to form sodium' hydroxid' freeing hydrogen. The

chlorin either unites with the water to form hydrochloric. acid or directly attacks the cathode where it is ireed, forming a chlorid of copper.

The current density and the resistance of the cell are such that considerable heat is generated. In the presence of the heat it appears that the cupric chlorid (CuCI in the presence of the metallic copper, formsouprous chlorid (CuCl.).f

It appears: that the.jcuprous chlorid is;

either hydrolyzed directly. by the hot water, giving red cuprous I 'OXld (Cu O), or it passes through'the: phase of forming the hydroxid of copper and then into. cuprous oxid. It appears that thechlorin which is thus liberated, unites with the. hydrogen of 1 the water to. form hydro-chloric acid and I then combines with the sodiumhydroxid to form salt and water, or the chlorin may funite with the sodium in some other manner.

The final action is that the water is broken up into hydrogen and oxygen, of which the hydrogen is freed at the anode and passes .Oflf into theatmosphere, while; the oxygen unites with the copper atoms to form the cup rous oxid.

he cuprous oxid forms a very fine red precipitate which ma be drawn ofl? periodically as byop'ening t e valve 6 and permitting a. part of the contents of the vat 4: to

run into the filter 9. The cuprous ox-id is filtered out to a great extent, the liquid then passing into the tank 12 and being pumped back into the vat 4. The cuprous oxid may then be washed off, preferably by hot water from the pipe 16 to free it from salt or sodium and at the same time to replenish the water which has been electrolyzed in the vat 4. p I find that a certainamount of cuprous hydroxid is formed in theelectrolytic' cell.

-ois

This is reduced by washing with hot water .or is reduced in the cell by the hot electro- 1 ts, to" the cuprous oxid; This is more "likely to be formed when the electrolyte is cold as when the cell is first started up.

It' will be seen that" the process is continuous.

The reversing switch 7 is reversed peri way? of pipe 20.

odically to reverse-the clarity of the elec} trodes 1 and 2. I find t at this very greatly improves the operation of the electrolytic cell. The time of reversal may, of course,

" be varied considerably, and I give the figure of one hour merely as illustrative of a successful nianner of operating the device.

The next step in the process consists in mixing. the cuprous mud, in the wet form,

with graphite. This step is illustrated dia-,

grammaticall Fig. 2. The wet" mixing of the oxid with graphite substantially eliminates fiying'particles ofdiie graphite or of the. oxid. It also permitso a more thorough and even mixtnre' When it is desired .to .form metal brushes, the proportion of cuprous oxid to graphite is taken such that when the same is red'uced to the metal by ffiring, as willbedescribed later, the metal will be present in substantially the proportionof90%. The nextstepfafter mixing, the graphite and cuprous oxid istofire the same to re- ..ducethe oxid to the metal. This is done in v aclosed furnace as shown in'Fig. 3 with a 'rieducingatmosphere 18. The mix 17 is by way of the. pipe 19 and passes out by The firing chamber is heated to about 1500 deg. F. p

Where it is desired to make metal graphite brushes, a binder such as pitch is mixed with the metal graphite mix so that the pitch represents about 20% by weight of the batch. The proportions may, of course, be varied within wide limits. Where the pitch is employed as a binder, I-have found 1 it advantageous to give the material a preliminary baking, which I call a .pre-bake, to

drive off the low volatile constituents of the Q pitch; The pre-bake drives off a relatively "large "amount of the hydrocarbons that volatilizeat a temperature of between 200 de F. and 900 deg. F.

placed in the firing chamber in a current of hydrogen, city gas, or the like, which enters ufiicient. hydrocarbons of higher volatilizingtemperatures remain to give the necessary binding qualities of the material. This step of pre-bakin'g may also be applied to the manufacture of .other forms of brushes where a binder such as pitch is employed. Y

of material is placed in a closed The batch firing chamber 'such as that shown in Fig.

3, in a reducing atmosphere which may consist of hydrogen, city gas or the like. A

current of such gas is preferably passed through the firing chamber. The chamber is then subjected to a heat of substantially.

of nitrogen, could be employed. When the material is thus subjected to pre-baking only the more easily volatile hydro-carbons are driven off and certain others remain to deposit fixed carbon when the brush material is finally fired, as will be described later.

I have found that'this step of prebaking the material is highly useful, not only in the manufacture of composition brushes, but is also of great utility in the manufacture of plain carbon brushes.

When a metal brush is to be made the step-of mixing the binder and pre-baking is omitted. I

The material, after mixin reducing and pre-baking is then molded into suitable plates or blocks. If desired, the material may be. ground or passed through asleve to insure that the same is sufficiently pulver-- ized. The material is then placed in a suitable mold and subjected to hydraulic presv sure as indicated in Fig. 4 to form the mass into solid coherent form. The pressure applied is approximately 20 tons per square inch. This step is well understood by those skilled in the art. It-brings the particles of graphite and of metal, and "also the binder when it"is used, into very intimate relation. The blocks or slabs 21 are then placed in the closed furnace chamber 22 and fired in a reducing atmosphere, 23, which is maintained by passing a current ofhydrogen or gas in through the tube 24 and out at the tube 25.

In the firing chamber 23 the material is subjected to a heat sufficient to sinter the particles of metal together in the body of the brush. I have foundthat a temperature of I600 deg. F. will be sufiiciently high to secure this action. 'This temperature may be varied.

I have found that a denser and more homogeneous brush is produced'by the above rocess than, has. heretofore .been possible. he fineness of the metallic material secures .very important results in the different stages of manufacture. The mixture of the wet 'cuprous oxid with graphite is a verydistinct.

advantage in that the danger and discomfort from the flying dust or powder vis greatly reduced, being practically eliminated. Due to the fineness of the material,

' a better mixingis possible. 55

The? fineness'of the copper in the reduced form in the finishedbrushfisof great advantage in providing a smooth compact grain and a more dense and coherent structure than has heretofore been possible.

These particles of copper are extremely small, readily passing througha 200 mesh screen.- The particles of copper are m 0c tahedral form, which permits the flake particles of graphite to envelop'the copper particles much better than if both the graphite vention.

and copper were in flake form and thus a better structure and better bonding between particles is secured than in the brushes of the prior art.

The metal graphite brush has a greater density and lower specific resistance than a the prior art for the same metal content. The contact resistance between the brush. and commutator remains substantially the sameas a brush made by the prior art.

In the case of the metal brush I have discovered that the brush after it is finally brush of the same type made according to r baked may be placed back in the die and subjected to substantially the same pressure above mentioned and a very decided increase what the chemical reactions of the zinc, tin, 90.

nickel, etc., of the alloy are,but I find by actual trial that the alloys may be handled in all respects like the copper without any variation in the divided metal with the exception. of a small loss in the case of tin which appears not togo out of the electrolyte in quite the same degree as the other metals' r It is possible, as I have found, to applythe same electrolytic process to the manufacture of oxids of other metal, particularly manganese. 7

Finely divided metals, 'such as copper and zinc or tin, etc.,- secured from any source,.

may be mixed and fired in a reducing atmosphere to substantially '1500 deg.. secure-finely divided or powdered alloy without the necessity of melting into a mass and repulverizing. This is an important fea-v ture of myinvention and may be practised with or without an excess of carbon.

' I do not intend to be limited to the pre cise details or ranges set out in the above specificationsas considerable latitude is perm1ss1ble and considerable variation ispossito I ble' while still gaining the benefits of myinlclai'mz" 1'. A brush of the classdes'cribed consisting of a mixture offinely subdivided metal containing copper, with powdered graphite,

said mixture being bonded together solely .by pressure.

2. A brush of the Cass described, 'consisting of a mixture of metal containing copper,

said metal being in the form of minute crystals capable of passing a 200 mesh screen,

and powdered graphite, said metal crystals entermg into te mixture in substantially the proportion of 90% and the graphite en- .sure to bond together into a dense, close grained, coherent mass having1 substantially the appearance and'color of t e metal.

3. The method of making brushes for'electrical machinery. which comprises electrically precipitating cuprous oxid,- then mixing the cuprous oxid in a wet condition" wlth I I class descrlbed whlch comprises preclpitatpowdered-graphite,"and then firing the mix ture in. a reducing atmosphere to reduce the oxid to the metal.

4,1 The method of manufacturing brushesi v of the rigid block type, which consists in mixing cuprous oxid with powdered graphiite in substantially the final proportion of graphite to'90% metal byweight, then "firing-to reduce the cuprous oxid to copper,

then compressing the mixture to cause 00- .hesion.

5. Themethod of manufacturing brushes of' 'the rigid block type, which consists in precipitating cuprous'oxid, mixing the same wet with graphite, then firing'the same to reduce the cuprous oxid to the metal, then compressing the mixture. v

6. The method of forming finely divided metal for the manufacture of brushes, which consists in precipitating an'joxid of copper from a solution-of a chlorid of copper to produce a finely sub-divided oxid, then fir-' ing the same to reduce the oxid of copper to finely divided copper. 7 The method of making a brush'which comprises mixing precipitated metal oxid. with graphlte in finely divided form, firing.

to reduce the oxid to elemental metal, .then compressing the mixture to bond.

r 8. The method vof making a brush which comprises mixing precipitated metal 'oxid with graphite in finely divided form and "an excess of carbon in powdered form and :then firing to reduce the oxid to the elemental metalvwithin the mass of carbon.

'10; The method of forming a brush of the inganroxid of a metal, mixing the same H with graphite, firing the mixture in a nonoxidizing atmosphere to reduce the oxid of the metal to finely divided particles of the metal, compacting the mixture into a dense coherent mass, Yagain firing the mass in anon-oxidizing atmosphere, and-again compressingqthe mass to increase the density thereof.v

11.- The me hod of making a brush of the above described type, which comprises, mix- .ing cuprous oxid in minutely sub-divided form while .Wet with powdered graphite, then firing the ,gmixture 'to reduce the cuprous oxid to metal inthe form of exceedingly finely crystals throughout the mixture, and then compressing the mixture to cause 'the particles of graphite and-the crystals of metal to bond-,and firing the-compressed and bonded mass; j

12. A brush'of the rigid blocks type, com--- prising a mechanical mixture of graphite in powdered form and exceedingly 'fine'particles of metal'comprising copper, said crystals of metal being produced by reducing a precipitated oxid of the metal within the mass of graphite before the brush is molded.

In witness whereofv I hereunto subscribe my name this:.4=th day of April, A. D'. 1918.

HUGH H. 1 

